Effect of Crystal Fields in $Ho_{1-x}Dy_xNi_2B_2C$

From the anisotropy and the temperature dependence of magnetic susceptibilities of $Ho_{1-x}Dy_xNi_2B_2C$ system with magnetic field H perpendicular or parallel to c-axis, the crystalline electric field (CEF) effect has been studied and the magnetic exchange interaction constant $J_{ex}$ of rare-earth ions perpendicular to the c-axis estimated for 0 $\le $x$\le $1. The crystalline electric field parameter, $B_{02}$, the first Steven parameter and the most dominant term in this system, are determined from the high-temperature-limit anisotropic Weiss temperatures of the magnetic susceptibilities and there is a broad minimum around x $\sim $ 0.3, where superconducting transition temperature, T$_{C}$, and N\'eel temperature, T$_{N}$, are almost same.